The present invention relates to concentrated, liquid herbicidal compositions and the use thereof in a granular herbicide. More particularly, the present invention relates to a liquid herbicidal composition comprising (a) a first herbicide having an acid functionality in the form of a low volatile ester, (b) a solid second herbicide comprising (i) fluroxypyr in the form of a free acid and/or as a solid ester and, optionally, (ii) an herbicide having an acid functionality in the form of a free acid, and (c) an aprotic solvent. The herbicidal composition is applied to a solid substrate to provide a granular herbicide. The substrate comprises an inert material, like a clay, a fertilizer material, or a mixture thereof.
Granular herbicides are important commercial products because of their ability to eliminate undesirable vegetation and their ease of application, either by hand or mechanical means. The granular herbicide can be an herbicide applied to an inert material, like clay or ground corn cobs, or can be a combination fertilizer/herbicide, wherein the herbicide is applied to a fertilizer material, i.e., a xe2x80x9cweed and feedxe2x80x9d composition.
In a granular form, an herbicide is impregnated into or absorbed onto an inert material or a fertilizer material. In the granular form, the herbicide product is supplied in a plastic bag, a plastic drum, or a fiber keg. The granular herbicide product is applied to vegetation by directly spreading the herbicide impregnated granules onto the vegetation at a suitable dosage rate.
It is known that certain compounds, like substituted benzoic acid herbicides and phenoxy-substituted carboxylic acid herbicides, possess selective herbicidal activity against broadleaf vegetation at dosages as low as a few ounces of active herbicide per acre. Accordingly, such herbicides are especially useful in eliminating unwanted vegetation from ornamental turf.
Solid substituted benzoic acid and the phenoxy-substituted carboxylic acid herbicides, and other solid herbicides having a carboxylic acid functionality in a free acid form or an ester form have been applied to susceptible vegetation, but herbicidal effectiveness is relatively poor because the water-insoluble form of these solid herbicides does not sufficiently penetrate the leaves of susceptible vegetation for fast and efficient eradication. In addition, application of such herbicides to a solid substrate is difficult because the free acid form and certain ester forms are solids. Therefore, the solid free acid and ester forms of these herbicides either must be applied to a solid substrate from a solution, which requires solvent removal or absorption of the solvent onto an adsorbent and/or drying agent to provide a dry granular herbicide. Alternatively, to avoid solvents, the solid forms of the herbicide must be applied as either a very finely ground powder or a melt, which requires an expensive heating step and more complex grinding, heating, and application apparatus and processes.
To improve performance, the substituted benzoic acid herbicides and the phenoxy-substituted carboxylic acid herbicides, and other solid herbicidal compounds having an acid functionality, traditionally are converted from the free acid form to a liquid ester form or to a salt form. The salt and liquid ester forms have enhanced water solubility and leaf penetration properties. Both the liquid ester form and the salt form of these herbicidal compounds are available commercially, and are provided as liquid products containing a known, but variable, amount of the active herbicide. For concentrated products, a predetermined amount of water is added to dilute the active herbicide before spraying susceptible vegetation. The predetermined amount of water is related to the concentration of the active herbicide in the liquid herbicidal product and the desired strength of the spraying solution.
In general, the ester forms of these herbicides are provided as petroleum distillate-based emulsifiable concentrates that are diluted with water. The resulting herbicide emulsion then is sprayed on the vegetation to be controlled.
For reasons of economy and safety to the environment and the herbicide applicator, the salt forms of an herbicide often are the preferred form of these herbicides. The salt forms of these herbicides are provided as concentrated aqueous solutions that are diluted with water. However, some water-soluble, solid forms of the salt form of these herbicidal compounds also are available. The solid forms typically are water-soluble, solid products containing essentially only the herbicide (see Champion et al. U.S. Pat. No. 5,266,553), as opposed to water-insoluble granular products. Also, see Flahine U.S. Pat. No. 5,965,487, and Mulqueen et al. U.S. Pat. Nos. 5,374,603 and 5,436,223.
In addition, granule herbicides are prepared by impregnating a substrate with a highly concentrated aqueous solution of the herbicide salt, which often requires the addition of expensive drying agents, such a corn cob granules or silica, in order to provide a noncaking, dry granular herbicide. The highly concentrated aqueous solution of the herbicide salt used to make the granule herbicide tend to form crystals when stored at relatively cool temperatures, i.e., at temperatures below 40xc2x0 F. Because the majority of granular herbicide manufacturing is done during the winter months, special heating and mixing of the aqueous herbicide concentrates prior to application onto the substrate is necessary to assure that the substrate is impregnated with the precise loading required by U.S. federal regulations.
The ester and salt forms of herbicides containing an acid functionality traditionally are applied to solid substrates, but suffer in cost and difficulty of manufacture because of the previously mentioned problems of solvent removal, and the need to utilize expensive drying agents. In addition, applying a salt form of the herbicide to a substrate often is not practical or feasible. First, applying an aqueous solution of the salt form of an herbicide to a water-soluble substrate wets substrate surfaces and makes processing difficult. Second, a solid salt form of an herbicide is difficult to apply, and especially to apply evenly, to a solid substrate. In addition, granular herbicides manufactured by adding a solid salt form of an herbicide to a substrate are hygroscopic, which causes clumping and stickiness, and requires addition of a drying agent to the composition.
Therefore, it would be advantageous to provide a highly concentrated, liquid herbicidal composition that can be applied directly to a solid substrate, without dilution or addition of drying agents, to provide a granular herbicide containing the desired herbicide combination in the desired amounts. The concentrated liquid herbicidal composition avoids the need to apply an herbicide solution or a molten herbicide to a substrate, which reduces manufacturing costs and equipment associated with preparing an herbicide solution or melting a solid herbicide, applying the molten herbicide to a solid substrate, and evaporating solvent. It also would be advantageous to provide a concentrated liquid herbicidal composition that exhibits excellent cold storage stability, and can be applied at relatively cool temperatures, compared to present-day herbicidal compositions applied to a granular substrate.
The present invention is directed to concentrated, liquid herbicidal compositions. The concentrated herbicidal compositions are used in undiluted form to prepare granular herbicides.
More particularly, the present invention is directed to a concentrated, liquid herbicidal composition comprising (a) a first herbicide having an acid functionality in the form of a low volatile ester, (b) a solid second herbicide comprising (i) fluroxypyr in the form of a free acid and/or as a solid ester, and, optionally, (ii) an herbicide having an acid functionality in the form of a free acid, and (c) an aprotic solvent. The composition comprises about 55% to about 85%, by weight, of the first herbicide, about 6% to about 35%, by weight, of the solid second herbicide, and about 1% to about 10%, by weight, of the aprotic solvent.
As used herein, the term xe2x80x9cacid functionalityxe2x80x9d is defined to include a carboxylic acid functionality (CO2H) and a phenolic functionality (OH).
The term xe2x80x9csolid ester formxe2x80x9d is defined as an ester of fluroxypyr, or an ester of other carboxylic acid containing herbicides, having a melting point of greater than 25xc2x0 C. at 760 mm pressure.
The concentrated herbicidal composition is used in the manufacture of a granular herbicide. As used herein, the term xe2x80x9cgranular herbicidexe2x80x9d is defined as an herbicide or mixture of herbicides absorbed, impregnated, or coated onto a solid substrate. The solid substrate can be an inert material, e.g., a clay, and/or can be a fertilizer material, e.g., urea/formaldehyde fertilizers, urea, potassium chloride, ammonium compounds, phosphorus compounds, sulfur, similar plant nutrients and micronutrients, and mixtures and combinations thereof, both synthetic and naturally occurring organic and inorganic materials.
Therefore, one aspect of the present invention is to provide a highly concentrated, liquid herbicidal composition. Another aspect of the present invention is to utilize the herbicidal composition, without dilution, in the preparation of a granular herbicide.
Yet another aspect of the present invention is to provide a liquid herbicidal composition consisting essentially of the first herbicide, the solid second herbicide, and the aprotic solvent, in the form of a homogeneous liquid. The herbicidal composition is free, or at least essentially free, of a protic solvent, such as an alcohol or a glycol. The absence of a protic solvent prevents the undesirable formation of esters of the solid second herbicide.
Another aspect of the present invention is to provide a method of preparing a granular herbicide comprising the step of applying the undiluted herbicidal composition to the surfaces of a solid substrate. The method optionally comprises a step of heating the herbicidal composition at a temperature of about 80xc2x0 F. to about 100xc2x0 F. to improve the flow and spray properties of the herbicidal composition, and thereby facilitate application of the herbicidal composition to the substrate, as opposed to solubilizing a solid present in the herbicidal composition.
Yet another aspect of the present invention is to provide a liquid herbicidal composition comprising (a) a first herbicide (low volatile ester form), (b) a solid second herbicide comprising (i) fluroxypyr in the form of a free acid and/or as a solid ester, and optionally, (ii) an herbicide having an acid functionality free acid form independently selected from (a) a substituted benzoic acid herbicide, especially methoxy-substituted or halogen-substituted benzoic acid herbicides; (b) a phenoxy-substituted carboxylic acid herbicide, especially chlorophenoxy-substituted carboxylic acid herbicides; (c) herbicides having a nitrogen-containing heterocyclic ring and a carboxylic acid functionality, especially substituted picolinic acid and pyridine containing herbicides; and (d) miscellaneous herbicides having an acid functionality. The first, second, and optional herbicides, independently, can be, for example, triclopyr, clopyralid, 2,4-dichlorophenoxyacetic acid (2,4-D), 2-(2,4-di -chlorophenoxy)propionic acid (2,4-DP), 2,4-dichloro-phenoxybutyric acid (2,4-DB), 2-methyl-4-chlorophen-oxyacetic acid (MCPA), 2-(2-methyl-4-chlorophenoxy)-propionic acid (MCPP), 2-methyl-4-chlorophenoxy-butyric acid (MCPB), endothall, glufosinate, glyphosate, picloram, bromoxynil, carfentrazone, and mixtures thereof. At least a portion of the second herbicide comprises fluroxypyr, in the form of a free acid or a solid ester.
The above and other aspects and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments.